A system controls the air-fuel ratio in an exhaust gas supplied from an internal combustion engine to a catalytic converter in order to keep an output voltage Vout of an O2 sensor disposed downstream of the catalytic converter at a predetermined target value Vop. In the system, the temperature of an active element of the O2 sensor is controlled at a predetermined temperature such that the output voltage of the O2 sensor at an inflection point of output characteristics thereof is substantially the same as the target value Vop.
Legal claims defining the scope of protection, as filed with the USPTO.
1. An O 2 sensor in a system for controlling an air-fuel ratio in an exhaust gas supplied from an internal combustion engine to a catalytic converter disposed in an exhaust passage of the internal combustion engine for keeping an output voltage of the O 2 sensor at a predetermined target value to achieve a predetermined exhaust gas purifying capability of the catalytic converter, said O 2 sensor being disposed in the exhaust passage downstream of said catalytic converter for generating an output voltage having a level depending on the concentration of oxygen in the exhaust gas, said output voltage changing with respect to the air-fuel ratio in the exhaust gas which is represented by the concentration of oxygen, at a gradient which switches from a large gradient to a small gradient via an inflection point as said air-fuel ratio turns richer, said O 2 sensor having such output characteristics that the output voltage thereof at said inflection point is substantially the same as said target value.
2. An O 2 sensor according to claim 1 , wherein said output characteristics of said O 2 sensor are achieved by controlling the temperature of an active element of the O 2 sensor at a predetermined temperature.
3. An O 2 sensor according to claim 2 , wherein said predetermined temperature is equal to or higher than 750 C.
4. An apparatus for controlling an air-fuel ratio in an exhaust gas supplied from an internal combustion engine to a catalytic converter disposed in an exhaust passage of the internal combustion engine for keeping an output voltage of an O 2 sensor at a predetermined target value to achieve a predetermined exhaust gas purifying capability of the catalytic converter, said O 2 sensor being disposed in the exhaust passage downstream of said catalytic converter for generating an output voltage having a level depending on the concentration of oxygen in the exhaust gas, said apparatus comprising: sensor temperature control means for controlling the temperature of an active element of the O 2 sensor responsive to the temperature of the exhaust gas so as to be kept at a predetermined temperature.
5. An apparatus according to claim 4 , wherein said predetermined temperature is equal to or higher than 750 C.
6. An apparatus according to claim 4 or 5 , wherein said O 2 sensor comprises a sensor for generating an output voltage which changes with respect to the air-fuel ratio in the exhaust gas which is represented by the concentration of oxygen, at a gradient which switches from a large gradient to a small gradient via an inflection point as said air-fuel ratio turns richer, said predetermined temperature being a temperature which is determined such that the output voltage of said O 2 sensor at said inflection point is substantially the same as said target value when the temperature of the active element of the O 2 sensor is kept at said temperature.
7. An apparatus according to claim 4 , wherein said sensor temperature control means comprises controlling means for controlling the temperature of said O 2 sensor at a temperature lower than said predetermined temperature until a pre-determined period of time elapses after said internal combustion engine has started.
8. An apparatus according to claim 4 , wherein said sensor temperature control means comprises controlling means for controlling the temperature of the active element of the O 2 sensor with an electric heater, and de-energizing said electric heater when the temperature of said electric heater is in excess of a predetermined upper limit.
9. A method of controlling an air-fuel ratio in an exhaust gas supplied from an internal combustion engine to a catalytic converter disposed in an exhaust passage of the internal combustion engine for keeping an output voltage of an O 2 sensor at a predetermined target value to achieve a predetermined exhaust gas purifying capability of the catalytic converter, said O 2 sensor being disposed in the exhaust passage downstream of said catalytic converter for generating an output voltage having a level depending on the concentration of oxygen in the exhaust gas, said method comprising the step of: controlling the temperature of an active element of the O 2 sensor responsive to the temperature of the exhaust gas so as to be kept at a predetermined temperature when the air-fuel ratio in the exhaust gas is controlled.
10. A method according to claim 9 , wherein said predetermined temperature is equal to or higher than 750 C.
11. A method according to claim 9 , wherein said O 2 sensor comprises a sensor for generating an output voltage which changes with respect to the air-fuel ratio in the exhaust gas which is represented by the concentration of oxygen, at a gradient which switches from a large gradient to a small gradient via an inflection point as said air-fuel ratio turns richer, said predetermined temperature being a temperature which is determined such that the output voltage of said O 2 sensor at said inflection point is substantially the same as said target value when the temperature of the active element of the O 2 sensor is kept at said temperature.
12. A method according to claim 9 , further comprising the step of controlling the temperature of said O 2 sensor at a temperature lower than said predetermined temperature until a predetermined period of time elapses after said internal combustion engine has started.
13. A method according to claim 9 , wherein the temperature of the active element of the O 2 sensor can be controlled by an electric heater, further comprising the step of de-energizing said electric heater when the temperature of said electric heater is in excess of a predetermined upper limit.
14. A recording medium readable by a computer and storing an air-fuel ratio control program for enabling said computer to perform, in a system having an O 2 sensor disposed in an exhaust passage of an internal combustion engine downstream of a catalytic converter disposed in said exhaust passage, for generating an output voltage having a level depending on the concentration of oxygen in an exhaust gas supplied from said internal combustion engine through said exhaust passage to said catalytic converter, a process of controlling an air-fuel ratio in the exhaust gas for keeping an output voltage of the O 2 sensor at a predetermined target value to achieve a predetermined exhaust gas purifying capability of the catalytic converter, said air-fuel ratio control program comprising a program for enabling said computer to perform a process of controlling the temperature of an active element of the O 2 sensor responsive to the temperature of the exhaust gas so as to be kept at a predetermined temperature when the air-fuel ratio in the exhaust gas is controlled.
15. A recording medium according to claim 14 , wherein said predetermined temperature is equal to or higher than 750 C.
16. A recording medium according to claim 14 , wherein said O 2 sensor comprises a sensor for generating an output voltage which changes with respect to the air-fuel ratio in the exhaust gas which is represented by the concentration of oxygen, at a gradient which switches from a large gradient to a small gradient via an inflection point as said air-fuel ratio turns richer, said predetermined temperature being a temperature which is determined such that the output voltage of said O 2 sensor at said inflection point is substantially the same as said target value when the temperature of the active element of the O 2 sensor is kept at said temperature.
17. A recording medium according to claim 14 , wherein said air-fuel ratio control program comprises a program for enabling said computer to perform a process of controlling the temperature of said O 2 sensor at a temperature lower than said predetermined temperature until a predetermined period of time elapses after said internal combustion engine has started.
18. A recording medium according to claim 14 , wherein the temperature of the active element of the O 2 sensor can be controlled by an electric heater, said air-fuel ratio control program comprising a program for enabling said computer to perform a process of de-energizing said electric heater when the temperature of said electric heater is in excess of a predetermined upper limit.
Cooperative Patent Classification codes for this invention. Click any code to explore related patents in that topic.
February 14, 2003
November 9, 2004
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